The strong interaction or strong nuclear force is one of the four fundamental forces in physics.

The other fundamental forces are electromagnetism, the weak interaction, and gravitation. They are called fundamental because there is no simpler way for physicists to understand what the forces do or how they do it.

The strong nuclear force is what holds most ordinary matter together. It does this in two ways: it holds subatomic particles, like neutrons and protons, together, and then it holds the atomic nucleus together.